The molecular mechanisms of the development of the sensitive interacting hormonal and nonhormonal control of liver glycogen metabolism will be investigated. The catalytic and regulatory properties of liver glycogen synthases and phosphorylase in fetal, neonatal and developing rats will be characterized in conjunction with a study of the development of the hormone-sensitive glycogen synthase phosphatase that is functional in adults but nonfunctional in neonatal rats in the absence of nutritional factors. In addition, the molecular properties of the synthase from developing rat will be described in terms of the requirements essential for a phosphoprotein substrate interaction with interconverting enzymes concerned with covalent modification of the synthase.